Python script to add additional faces to an existing mesh
I would not say "simple".  With an understanding of how you constructed the mesh in question it would probably be possible to algorithmically generate the vertex indices for the new faces.

Without the algorithm all I can supply to you is the basic code of how to add faces to an existing mesh:

Here is an extract from http://web.purplefrog.com/~thoth/blender/python-cookbook/add-to-mesh.html that illustrates several idioms for modifying a mesh using bmesh.  You are chiefly interested in the bm.faces.new( vertex_index_array ) technique.

import bpy
import bmesh


def mission1(scn):

    obj = scn.objects.active
    if bpy.context.mode == 'EDIT_MESH':
        bm = bmesh.from_edit_mesh(obj.data)
    else:
        bm = bmesh.new()
        bm.from_object(obj, scn)

    v2 = bm.verts.new( [0,7,0] )

    bm.verts.ensure_lookup_table()

    v1 = bm.verts[3]

    e1 = bm.edges.new( [v1, v2] )

    f1 = bm.faces.new( [v1, v2, bm.verts[7]])

    if bpy.context.mode == 'EDIT_MESH':
        bmesh.update_edit_mesh(obj.data)
    else:
        bm.to_mesh(obj.data)

    obj.data.update()

mission1(bpy.context.scene)


If you are willing to try without python, consider using Bridge Edge Loops:  How can I automatically create edges according to the number of vertices?